The present invention relates to a new cyanine dye having a maximum absorption wavelength in the near infrared region, and an optical information recording medium employing the cyanine dye, and more particularly to a cyanine dye which is useful as a material for an optical information recording medium for recording information therein by means of a laser beam, and reproducing the recorded information therefrom by detecting the changes in the quantity of light reflected thereby, and to an optical information recording medium comprising a substrate and a recording layer comprising the cyanine dye.
Conventionally, an optical information recording medium having a thin film recording layer in which a cyanine dye is used is proposed, for example, in Japanese Laid-Open Patent Application No. 59-85791. The recording medium which uses the cyanine dye has an especially large absorption coefficient as compared with other dyes showing absorption in the near infrared range, so that its recording and reproduction sensitivity and S/N are high. In addition, it has high storage capabilities. This recording medium can be formed by using a variety of methods such as vaporizing or coating a thin film including the cyanine dye onto a substrate. The formation of a thin film by the coating method can be said to be an especially industrially advantageous method compared to other methods. However, a process must be used in which the cyanine dye is dissolved in an organic solvent to obtain a coating liquid. However conventionally known cyanine dyes including the above cyanine dye have low solubility in organic solvents and lack stability, so that the dispersibility and stability of the cyanine dyes in the dissolving process is poor. When such cyanine dyes are employed, the reproducibility of the recording and the storage capabilities of the recording medium are inadequate.